In recent years, portable handheld ultrasound imaging systems such as the ones described in U.S. Pat. No. 6,540,682 and U.S. Pat. No. 6,106,472 have been widely adopted in medical healthcare markets, especially point-of-care markets such as Emergency Medicine, Fertility, Surgery, and Anesthesia. However, due to the complexity of ultrasound imaging systems and the associated phase array transducers, manufacturing of these systems and transducers is very costly, resulting in expensive portable ultrasound systems. The high price limits the use of portable ultrasound imaging systems by many healthcare providers, and prevents them from becoming an imaging ‘stethoscope’, even though advanced technology allows a handheld ultrasound imaging system to be used at the point-of-care. A less complex, low cost handheld ultrasound imaging system will allow an ultrasound imaging system to become the imaging ‘stethoscope’ and become a basic tool in every area of the healthcare system. A mechanically focused single element imaging system may be a solution since no complex phased array and corresponding beamforming system are necessary. However, a single element imaging system limits the image detail resolution, and the use of a driving motor for scanning makes color flow imaging very difficult to implement in the conventional way. This invention provides solutions for the image resolution and color flow imaging issues associated with ultrasound imaging systems with mechanically focused and motor driven transducers.